I. Field
The following description relates generally to wireless communications, and more particularly to methods and apparatuses that facilitate operating a relay via a Multimedia Broadcast Single Frequency Network based backhaul link.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-signal-out or a multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min{NT, NR}. Each of the NS independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
A MIMO system supports a time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the access point to extract transmit beamforming gain on the forward link when multiple antennas are available at the access point.
With respect to LTE-Advanced (LTE-A) systems, it is noted that an economically attractive option for LTE-A relays is the in-band half-duplex relay, which switches between transmitting (Tx) and receiving (Rx) for access and backhaul links on each frequency band. Multimedia Broadcast Single Frequency Network (MBSFN) sub-frames enable the relay half-duplex downlink operation, where a relay transmits common reference signals and control signals (e.g., PCFICH (Physical Control Format Indicator Channel), PHICH (Physical Hybrid Automatic Repeat Request Indicator Channel), and/or PDCCH (Physical Downlink Control Channel) grants for uplink data (both legacy and non-legacy UEs), as well as PDCCH grants for downlink data (non-legacy UEs)) on the first and possibly the second Orthogonal Frequency Division Multiplexing (OFDM) symbols on the downlink, then switches to receive the donor cell transmission for the rest of the sub-frame. However, operating such a relay within a macro/relay cell environment introduces several potential issues. For instance, within such environment, it may be difficult for a user equipment to distinguish control symbols intended for legacy user equipment from control symbols intended for non-legacy user equipment. A method and apparatus for efficiently operating a relay via an MBSFN-based backhaul link is thus desirable, which addresses at least this potential issue. Moreover, it would be desirable to provide a method and apparatus that facilitates having a relay node receive legacy control information from a donor cell, wherein the control information occupies an initial set of symbols which collide with a relay node is transmission.
The above-described deficiencies of current wireless communication systems are merely intended to provide an overview of some of the problems of conventional systems, and are not intended to be exhaustive. Other problems with conventional systems and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.